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  • peatsatime
    replied
    Originally posted by Brando23 View Post
    Ok. Last question. Would lining the inside of the oven with very thin gauge stainless steel be an option? Would that at least keep out the nasty stuff from falling onto the food? If I could get 3-6 months of use out of this build I wouldnt be as pissed. The next oven will be done with much more research and with fire brick . Thanks so much and sorry for all the noob questions
    If you are able to flip it upside down, you can try what I did. I used castable refractory cement from home depot and put 1/2" layer inside the dome. I've brought it up to full temp a dozen or so times and it's holding up so far. Any areas that did not have it just disintegrated, so went back and covered those as well.

    I am another victim of all the diy info out there for casting. Unfortunately I found this forum far too late after i finished my build, but I will say so far it's been working out great. Knowing what I know now, I would have gone a different direction I think. I'll make a thread on mine at some point, but it's the infamous inflatable ball method as well...lol.

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  • david s
    replied
    Forming against a compound curve with flat stainless would be a challenge.

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  • Brando23
    replied
    Ok. Last question. Would lining the inside of the oven with very thin gauge stainless steel be an option? Would that at least keep out the nasty stuff from falling onto the food? If I could get 3-6 months of use out of this build I wouldnt be as pissed. The next oven will be done with much more research and with fire brick . Thanks so much and sorry for all the noob questions

    Leave a comment:


  • david s
    replied
    Clay/sand contains no cementious material and if applied in a thin layer is more likely to crack and flake off, IMO, especially because you are increasing the proportion of clay which shrinks.

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  • Brando23
    replied
    Thank you for the prompt reply and advise. I attached some photos. I have not fired the oven yet. The first two weeks it was covered with a damp bed sheet. It was uncovered for two weeks, removed the yoga ball and then I applied the fireclay outer layer. I can get to the interior fairly easily to apply a layer over the perlite. Would a clay/sand mixture be an option ?

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  • david s
    replied
    Hi Brando,
    it sounds like you have already dried and fired the oven in which case adding a layer to the inside will be difficult. Not only will it be hard to get in there and apply it, there are problems with bonding onto a dry surface. The surface should be damp, but not wet, so there is a reduced suction of water from the material applied to it. If the water is sucked out of the material being applied there will not be enough for the chemical process of hydration to take place. Additionally, the material will require extended damp curing for at least a week in the case of Portland cement and a min of 24 hrs for CAC. This maybe difficult if not impossible for you to achieve. Also any thin layer is more likely to be more vulnerable to cracking and flaking. After the operation the oven will have to be slowly dried again or the sudden water removal can create problems. By all means give it a go, you may be successfu, but I wouldnít be too hopeful. Good luck.
    Dave
    Last edited by david s; 05-11-2019, 02:16 PM.

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  • Brando23
    replied
    Hello, I also fell into the "quick and easy" perlite oven on YouTube. Basically I did more research during the build and realized that a lot of these perlite ovens are not very durable or even safe. I am trying to salvage the project though and i made a home brew fireclay cement to cover the top of the perlite cement mold and too fix a crack . Now I would like to apply something to the inside of the oven so that the perlite/cement doesn't get into our food. Would the 3:1:1:1 home brew work ? Or a store bought high heat refractory cement ? thanks for the advise

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  • CoastalPizza
    replied
    Originally posted by mkasap View Post
    ...Did you have any issues with those small holes on the dome after several fires?...
    No, none at all. They are only 1/4" (6 mm) diameter ó I just covered them with the rockwool batt insulation which was then covered in ~2" (50 mm) of perlcrete and then the render coat so they are fully blocked off from the outside.

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  • mkasap
    replied
    Good morning David. If my oven is going to have a total weight of around 350kg then most probably i will make second thoughts for the portable version as my backyard is mainly grass which will make the ovenís portability a nightmare. Itís sad because i collected all the materials needed and i wanted to start the construction now instead of waiting till we move to the new house. But seeing that a portable version wonít be really portable, unfortunately i have to wait till the end of November.

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  • david s
    replied
    Firstly it is more expensive to fabricate a steel stand and fit it with wheels. Moving the oven should not be a problem regards cracking although it is with a trailerable version. You do need to make sure the wheels are at least 100 mm diam (small wheels risk getting jammed and creating a dangerous capsize with around 350 kg falling about a metre), two of them swivelers and lockable (all these wheels have a load rating that shouldnít be exceeded). Forget trying to move it over rough surfaces or grass. The first steel stand I built was of 25 mm square rolled hollow section, but a fairly thin grade ( 1.2 mm from memory. It seemed plenty strong enough until I mounted the oven on it. I thought it had too much flex, but it still stands and is operating some nine years later without problems. I now use and recommend 4 mm thick 50 x 50 mm galvanised angle, which is much stronger. It is really far easier, stronger, safer and cheaper to build a masonry stand. The downside is that the oven canít be moved.

    Regarding the chicken wire, it wonít do much good in the vermicrete layer but would be useful over the top of it so the outer rendered shell will be reinforced by it. I gave up with this method years ago as it is quite time consuming. I now simply add random reinforcing fibres into the outer render when mixing.
    Last edited by david s; 01-05-2019, 01:13 AM.

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  • mkasap
    replied
    david s May i have your feedback please, regarding making my oven portable? Thank you.


    Originally posted by mkasap View Post
    Thank you very much for your long informative reply, thatís exactly the reason why iíve asked you specifically. Im taking your suggestions very seriously because after the perlcrete catastrophe i want to build something long-lasting but also eliminate any possible sources of contamination. My chicken wire is indeed very thin but iím not gonna risk it because i canít be sure that i will install it under the inner surface all over so, itís rejected. I will only use it in the insulation layer. Another concern i have is regarding making my oven portable. I want to create a metal base approx. 140x90x90cm (LxWxH) to build my oven on, with four heavy duty wheels. Do you think my oven will suffer from vibrations from moving it around the house, increasing the risk of cracking? Thanks again and im sorry for bombarding you with all these questions.

    Leave a comment:


  • mkasap
    replied
    Thank you very much CoastalPizza. Your oven looks rock solid - well done!! Did you have any issues with those small holes on the dome after several fires? Photos are saved for future reference
    Last edited by mkasap; 01-04-2019, 05:45 AM.

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  • CoastalPizza
    replied
    Originally posted by mkasap View Post
    ...create a vertical mould for the first 20-30cm of the dome and after 2-3 days continue building the rest of the dome based on the sand mould....
    This is exactly how I built mine - see the build thread link.
    Post #4 shows the finished ring mold
    Post #9 shows the cast ring after the mold is removed
    Post #10 shows the sand filling the ring and the casting of the domed top
    The casting was done using the 3:1:1:1 formula home-brew that David S recommends with about 2% by weight stainless steel needles added.
    I've started the build of my 32" home-brew cast oven. I've removed the sod from the area where I'll be pouring a 4" thick slab. I'm planning for the slab

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  • mkasap
    replied
    Thank you very much for your long informative reply, thatís exactly the reason why iíve asked you specifically. Im taking your suggestions very seriously because after the perlcrete catastrophe i want to build something long-lasting but also eliminate any possible sources of contamination. My chicken wire is indeed very thin but iím not gonna risk it because i canít be sure that i will install it under the inner surface all over so, itís rejected. I will only use it in the insulation layer. Another concern i have is regarding making my oven portable. I want to create a metal base approx. 140x90x90cm (LxWxH) to build my oven on, with four heavy duty wheels. Do you think my oven will suffer from vibrations from moving it around the house, increasing the risk of cracking? Thanks again and im sorry for bombarding you with all these questions.
    Last edited by mkasap; 01-04-2019, 10:14 PM.

    Leave a comment:


  • david s
    replied
    Originally posted by mkasap View Post
    Im thinking to create a vertical mould for the first 20-30cm of the dome and after 2-3 days continue building the rest of the dome based on the sand mould. Would it be a good idea to put a chicken mesh so i have a good bonding between the two parts or the heat will expand the metal mesh and crack my dome?
    Chicken wire, being thin should not present problems from expansion because the greater surface area allows more heat dissipation than thicker steel. However, being coated with zinc which has a lower melting point than the oven might see, could be a problem. Once the protective coating has gone corrosion might start. Not sure though as the only way to tell would be to try it and break the oven apart after years of use. I tried using chicken wire reinforcing for the fourth oven I built and itís still operating ten years later, no idea what the condition of the chicken wire would be. Another consideration is that zinc vapours are highly toxic although being embedded in the middle of the casting should prevent release. The recommended reinforcing for castable refractory is melt extract fibres which are made of stainless steel. They are around 0.5 mm thick and being stainless are resistant to corrosion. I use them in the manufacture of my product, but they are not absolutely necessary. Most manufacturers donít use them as Iím sure theyíd advertise if they did; they are a pain to work with as the make handling the mix difficult as well as being expensive. Sorry about the long winded reply, but you did ask.
    Dave
    Last edited by david s; 01-03-2019, 02:14 PM.

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